Delay line for travelling wave tubes

ABSTRACT

A delay line for a travelling wave tube in the form of an interdigital line arranged in a hollow conductor and having coupling slots in partitions between line segments, utilizes additional tuned slots to destroy undesired interfering frequencies.

United States Patent 1151 3,707,646 Gross 14 1 Dec. 26, 1972 s41 DELAY LINE FOR TRAVELLING 3,309,630 3/1967 Hukunaga ..333/31 A WAVE TUBES 3,297,906 1/1967 Sphumacher... ..31s/3.s

3,233,139 2/1966 ChodorowJ. .l ..3l5/3.5 lnvemofl Franz r Mumch, Germany 3,171,054 2/1965 Dong et al ..31s/3.s [73] Assignee: Siemens-Aktiengesellschaft, B li 3,015,750 1/1962 Skowron et a1 ..315/3.5

and Mumch, Germany 1 OTHER PUBLICATIONS Filedi 1 1970 Power Travelling-Wave Tnbesfln J. F. G it t ins TK [211 App[ 102 7 7872 T7565 2 pps. 67-75 relied upon, Nov. 22, 1965.

1993M llias-wa qTyb 21bx1- wF- Giitins TK 7872T75G5C.2, Nov. 1965, pages 67-78. [30] Foreign Application Priority Data Jan. 14, 1970 Germany ..P 20 01 487.3 Primary Examiner-Herman Kart] Saalbach 1 Assistant Examiner-Saxfield Chatmon, J r. 1521 U.S. c1 ..31s/3.s, 333/31 A, 31513.6 Alwmeyflill, Sherman, Meroni, Gross & Simpson [51] Int. Cl ..H01j 25/34, 330 42 58 Field 61 Search ..315/3.5, 3.6, 39.3; 333/31 A ABSTRACT v A delay line for a travelling wave tube in the form of [56] References an inter-digital line arranged in a hollow conductor and having coupling slots in partitions between line UNITED STATES PATENTS segments, utilizes additional tuned slots to destroy un- 3,668,460 6/1972 James .......3l5/3.5 desired interfering frequencies, 3,205,398 9/1965 Allen et al..- ....3l5l3.5 3,453,491 7/1969 Cerko ..315/3.5 5 Claims, 2 Drawing Figures DELAY LINE FOR TRAVELLING WAVE TUBES BACKGROUND OF THE INVENTION 2. Field of the Invention This invention relates to a delay line for travellingwave tubes in the form of an interdigital line which is arranged in a hollow conductor with coupling slots between the individual line segments, which segments are formed by means of partitions which follow one another axially of the delay line.

2. Description of the Prior Art In order to prevent undesired interfering frequencies of a relatively high mode for such a delay line, it has been earlier proposed to select the dimensions of the coupling slots, which are directed diagonally to the axis of the delay line, in a way thatthe corresponding coupling-slot resonance is equal to the undesired frequency.

This method, which is very smooth in itself and which combines the measure for suppressing the interfering frequency directly with the coupling slots which are needed for other purposes, leads to difficulties in some cases, however, particularly when the diagonal dimensions of the coupling slots, which are tuned to the interfering frequency, lie outside of the measuring range for a reasonable operationalmode coupling.

SUMMARY OF THE INVENTION This invention has its primary object to provide a delay line arrangement with the help of which an optimum coupling can always be provided in the operational-frequency range, independent from the interfering frequency which is to be suppressed.

In order to realize this main objective, while generalizing the principle of the solution according to the above-described arrangement, additional slots are provided for a delay line of the above kind, in the partitions of the line segments which do not interfere with the operation a] mode and which are dimensioned in such a way that their resonant frequency is equal to an undersired interfering frequency of a higher mode of the line. Thereby, and with particular advantage, the additional slots are designed essentially dumbbellshaped.

The additional slots which, with tubes of relatively high efficiency, can also be applied with small beam caps surrounding the beam apertures have a relatively low impedance. They can be current-damped by means of a resistance layer or by means of a small damping dielectric plate which is arranged in the slot, loaded capacitively and field-damped to increase the band width of the selective damping.

BRIEF DESCRIPTION OF THE DRAWING Other objects, features and advantages of the invention will be best understood from the following detailed description, taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a longitudinal section al view through a por-' BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT A hollow conductor which surrounds the inter-digital structure is obtained in the illustrated sample embodiment by means of inserting a plurality of metal rings 1 alternately between a plurality of disks 2 which form the partitions of the delay line segment. Coupling openings 3 are formed in the disks 2 and are disposed on opposite sides alternately of the longitudinal axis of the delay line and small beam caps 5 surround the electron beam passage openings 4 which are provided in the individual partitions 2.

Additional slots 6 are inserted, according to this invention, in each partition 2, for instance by means of milling, and tuned to the frequency of an undesired higher interference mode of the line, so that the corresponding interfering frequency is destroyed by means of resonance in the slots, and transformed into heat. The illustrated dumbbell-shaped additional slots 6 which practically do not contribute at all to the coupling of the operational mode may also have squared or rectangular recesses (ends), in the place of the round sideward openings 7, or they may even consist of a slot only, which, if need be, may be in the shape of an arc.

The invention is not limited to the illustrated sample embodiment. It is, for instance, also possible besides another shaping of the additional slots 6 and besides providing damping layers and/or small dielectric plates in the slots to provide more than one additional slots 6 for each partition, which added slots would also be tuned to destroy undesirable frequencies.

Many other changes and modifications may be made in this invention by one skilled in the art without departing from the spirit and scope of the invention, and it is to be understood that I intend to include within the patent warranted hereon, all such changes and modifications as may reasonably and properly be included within the scope of my contribution to the art.

I claim as my invention 1. In a delay line for a travelling wave tube in the form of an inter-digital line having a plurality of axially aligned line segments including a series of aligned partitions within a hollow conductor, the partitions having coupling slots therein, the improvement comprising the provision of means in each of said partitions defining at least one additional slot of smaller size than the coupling slots, each said additional slot having a resonant frequency equal to an undesired interference frequency of a higher mode of the delay line and outside of the normal pass band of the delay line, and said additional slot being in a non-interference relationship with the spreading of the operational mode of the delay line.

2. In a delay line according to claim 1, wherein each of said means defines said additional slot as having a dumbbell shape.

3. In a delay line according to claim I, wherein each of said means includes a resistance layer covering the edges of the corresponding slot.

4. In a delay line according to claim 1, wherein each of said means includes a dielectric plate disposed in the corresponding slot.

5. In a delay line according to claim 4, wherein each of said means includes a resistance layer carried by said dielectric plate.

I060 I Z 0464 

1. In a delay line for a travelling wave tube in the form of an inter-digital line having a plurality of axially aligned line segments including a series of aligned partitions within a hollow conductor, the partitions having coupling slots therein, the improvement comprising the provision of means in each of said partitions defining at least one additional slot of smaller size than the coupling slots, each said additional slot having a resonant frequency equal to an undesired interference frequency of a higher mode of the delay line and outside of the normal pass band of the delay line, and said additional slot being in a noninterference relationship with the spreading of the operational mode of the delay line.
 2. In a delay line according to claim 1, wherein each of said means defines said additional slot as having a dumbbell shape.
 3. In a delay line according to claim 1, wherein each of said means includes a resistance layer covering the edges of the corresponding slot.
 4. In a delay line according to claim 1, wherein each of said means includes a dielectric plate disposed in the corresponding slot.
 5. In a delay line according to claim 4, wherein each of said means includes a resistance layer carried by said dielectric plate. 